Bugs show up on weather radar

This is a loop showing the National Weather Service weather radar in La Crosse, Wis., at 10:30 p.m. last night.

What is the green “storm” that pops up over the Mississippi River?

It’s bugs, perhaps mayflies, that hatch around this time every year.

The National Weather Service tweeted last night that this is a nightly occurrence lately.

We haven’t yet seen any images of a major hatch along the river, not like last year, anyway.

That’s not the case elsewhere in the Midwest. On Lake Erie, for example:

And along the Susquehanna River in Pennsylvania.

Mayflies live a short but famous life, spending most of their year as larvae. Once they hatch they make a big splash on Twitter for a night and then die. In their adult stage, they don’t have a mouth.

In other parts of the Midwest, mayflies have been hatching earlier this year. There have already been several hatchings in La Crosse this year.

If you’re out there with photos, La Crosse, let us know you’re OK.